When metals are treated in a furnace with a protective atmosphere of hydrocarbon gas, said gas is commonly converted from a raw gas material by an endothermic or exothermic gas generator which is provided independently from the furnace, and then supplied into the furnace.
In this invention, the raw gas material is supplied directly into the furnace without employing any such independent gas generator, wherein said raw gas material becomes within the furnace per se a converted gas which constitutes a protective atmosphere of said furnace, and whereby costs for producing the converted gas become extremely low since it does not employ any gas generator of the aforementioned kind, and costs for reheating the gas which has been converted in the gas generator and is being sent into the furnace are also saved.
Working principle of this invention is to provide a furnace with a plurality of curtains or walls which are made from a catalyst of metals or metal oxides and which extend within the furnace at locations outside of charging and discharging passages for articles to be treated in the furnace and adjacently to heating elements within the furnace so that they can effectively be heated. A raw gas material such as LPG, LNG, or urban gas which has been supplied into the furnace with air is changed, by its contact with the catalytic curtains or walls within the furnace, to heated and converted gas, under the protection of which metallic articles are heattreated.
Hence, this invention is to provide a furnace with protective atmosphere for heating metallic articles, in which a converted gas for producing said protective atmosphere is not formed by a gas generator which is independent to the furnace, but it is formed by supplying a mixture of LPG, natural gas, or urban gas with air directly into the furnace and by dissociating under heat said mixture gas by means of heating element and catalytic curtains or walls which are both provided within the furnace, to said protective atmosphere which is reductive for example for the effective heating or cementation of the metallic articles.